Electrical contact structures which extend through a substrate or a subarea of a substrate are becoming more and more important. Such contact structures which are also referred to as vias (vertical interconnect access) or through-connections facilitate the manufacture of space-saving components, for example. One possible design are metallic through-connections which are present in the form of electrical connections made of metal. It is usually strived for that the smallest possible through-connections or through-connections having small lateral dimensions are formed which have a relatively low volume resistance at the same time.
Conventional methods for manufacturing metallic through-connections, with the aid of which these objects are to be achieved, include the production of narrow holes or trenches having almost vertical walls in a substrate; the deposition of an insulating layer in the trenches; the opening of the insulating layer in a bottom area of the trenches; and, usually, the deposition of a diffusion barrier layer in the trenches. Subsequently, the trenches are filled up with a metal completely or partially.
The provision of the smallest possible lateral dimensions results in the through-connections, and thus the underlying trenches, having a relatively great aspect ratio (height/width ratio). This proves to be critical with regard to the above-described process sequence. For example, the insulating layer within the trenches may only be designed to have a relatively small layer thickness due to technical reasons. The greater the aspect ratio, the smaller is the producible layer thickness. The provision of greater aspect ratios, but also a greater insulation thickness, results in that opening the insulating layer on the bottom of the trenches is becoming increasingly more difficult. A greater aspect ratio is furthermore associated with the deposition of the diffusion barrier layer within the trenches becoming more difficult. Moreover, conventionally manufactured through-connections may lead to great mechanical stresses in a substrate. The cause thereof are differing thermal expansion coefficients of the metallically filled material and the surrounding substrate material (usually silicon).